OLED-devices are known from the state of the art. In general, an OLED-device consists at least of a first electrode material arranged on a carrier substrate, an organic optoelectronic active material deposited on the first electrode material, and a second electrode material covering at least partially the organic optoelectronic active material. One of the electrode materials acts as cathode layer, while the other electrode material acts as anode layer. As optoelectronic active material electroluminescenting materials, such as light emitting polymers, like e.g. poly(p-phenylenevinylene) (PPV), or light emitting low molecular weight materials, like e.g. aluminum tris (8-hydroxyquinoline).
As carrier substrate insulating materials, like e.g. glass or plastic can be used. As electrode material compounds like e.g. transparent conductive oxides (TCO), or metals, like e.g. copper, silver, gold, or aluminum can be used. It is also known from the state of the art to place a so called hole transporting layer between the electrode materials and the opto-electronic active material, like e.g. a PEDOT/PSS-layer (poly(3,4-ethylenedioxythiopene/polystyrolsulfonate) or a PANI/PSS-layer (polyaniline/polystyrolsulfonate), which lowering the injection barrier of the holes.
In operation, electricity is applied between the first electrode material layer and the second electrode material layer. The applied electricity causes an exited state of the optoelectronic active material by which relaxation to the non-exited state a photon is emitted. OLED-devices can be used, e.g. for displays or lighting.
To form large area OLED devices serial connected architectures are being used. To do so, it is known from the state of the art to manufacture interconnected OLED-devices by a process as described in the following.
As a first step, a substrate is manufactured in a patterning step. In this patterning step, a first electrode material is applied in pattern on a carrier substrate. The main function of this patterning step is to create electrically separated areas where later on the cathode and the anode will be electrically connected. This patterning can be done by e.g. depositing a functional layer by e.g. printing or sputtering through a shadow mask, etc.
In a subsequent step an OLED functional layer formed by an optoelectronic active material is applied. Small molecule functional layers are deposited by thermal evaporation in vacuum. The deposition of the organic material must be restricted in such a way that at least the cathode contacts are not coated. Usually, also the anode contacts are protected from the coating in order to achieve good electrical contacting later on. This structured deposition is achieved by means of a shadow mask. This mask is specific for each OLED design and is placed on top of the substrate during organic layer deposition. Masking can either be done in physical contact or with a small gap between the substrate and the mask. During the deposition process the shadow mask will be coated with the organic material.
In a next step a counter electrode is formed by deposition of a second electrode material layer. This is also applied in a vacuum thermal evaporation process. Also in this step the layer must be structured as otherwise a short circuit between the two electrode material layers, i.e. the cathode and the anode will occur. Also in this step the mask will be coated with material, wherein the cathode material typically is a metal like copper, silver, aluminum, gold, etc.
As the coated areas for organics and cathode are different a different set of masks must be used in every of the mentioned process steps.
If a serial connection of individual OLED-devices needs to be realized a very complicated set of shadow masks is required as the anode of a first OLED-device, e.g. a pixel, needs to be connected with the cathode of the next OLED-device. The minimum separation of individual OLED-devices is then determined by the alignment accuracy of the mask processes and the thermal expansion of the mask and the substrate during organics and cathode deposition. Therefore, the technique known from the state of the art has several drawbacks. As the masks are design specific a design change requires a new set of masks. This limits the throughput time for a design change and increases costs. The masks are coated during deposition. This requires regular cleaning and induces additional costs. Particles lost from the masks can lead to short circuits and reduce the yield of the production. The minimum feature size that can be realized is limited due to the thermal expansion of the masks and the alignment accuracy. This scales with the substrate size and is typically >200 μm. At least, the mask handling in vacuum is very expensive.